LABORATORY STUDIES AND DEMONSTRATIONS. 211 



thus live for months. L. terrestris may be obtained in great 

 numbers between April and November, by searching for them 



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.at night with a lantern in localities where numerous castings 



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show them to abound (a rather heavy but rich soil will be found 



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most productive). They will then be found extended from their 

 burrows, lying on the surface of the ground, and may be seized 



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with the lingers. Considerable dexterity is needed, and it is 

 necessary to tread very softly or the worms take alarm and in- 



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stantlv withdraw into their burrows. 



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For dissection fresh specimens are far preferable for most 

 purposes, though properly preserved ones answer the purpose. 

 Fresh specimens should be nearly killed by being placed for a 

 short time (about five minutes) in 70^ alcohol, and then stretched 

 out to their utmost extent in 50$ alcohol in a dissecting-pan, 

 the two ends being fastened by pins. They should then be at 

 once cut open along the middle dorsal line with scissors, the 

 Haps pinned out, and the dissection continued under the 50$ 

 alcohol. (They must be completely covered with the liquid.) 

 Bv this method the minutest details of structure mav be ob- 



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served, and many of the dissections should be done under a 



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watchmaker's lens. 



For preservation (every detail of which should be attended 

 to) a number of living worms are placed in a broad vessel filled 

 to a depth of about an inch with water. A little alcohol is then 

 cautiously dropped on the surface of the water at intervals until 

 the worms are stupefied and become perfectly motionless and re- 

 laxed (this may require an hour or two). They are then trans- 

 ferred to a large shallow vessel containing just enough 50$ 

 alcohol to cover them, and are carefully straightened out and 



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arranged side bv side. After an hour the weak alcohol is re- 



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placed by stronger (70$), which should be changed once or twice 

 at intervals of a few hours ; they are finally placed in J>< >/ 

 alcohol, which should be liberally used. The trouble demanded 

 by this method will lie fully repaid by the results. The worms 

 should be quite straight, fully extended, and plump, and they 

 may be used either for dissection or for microscopic study. 



For the purposes of section- cutting worms should be carefully 

 washed and placed in a moist vessel containing plenty of wet 

 filter-paper torn into shreds. The worms will devour the paper 7 



